Jay, my son is also 5 years old. The problem I've had with him in the past is that he was used to having his own way, and cried or claimed that "we don't love him," or "we're mean!" if we don't go along with him.
Our family has developed a daily routine for him, including TV time, outdoor time, indoor activity time, and time for him to choose a favorite activity. He also gets to earn "tickets" or "points" for good behavior or for doing small chores, eating all his dinner, or picking up his room which he can exchange for a fun treat. This is one way to help alleviate some of the tantrums.
Also, 5 year old are very precocious. This is the time that they are more verbally able to tell you what they think and feel, and communicate on a level with you that they weren't before. This is the point where they will test your patience, test their boundaries, and push you hard enough to make you cry. (DON'T STRESS!)
At this point, having a routine and being consistent in punishment/rewards will help reduce the tantrums. You also NEVER want to let your child see you cry or become upset, or they will realize what buttons to push with you. If you can't control your reactions, leave the room. Tell them that you are not going to listen to them behave that way, and go somewhere for a few minutes to get yourself in control. When you have control, return to the scene, and firmly take control of the situation. Yes, I do spank, but on rare occasions. If you do not spank, "time-out" is equally effective, provided you make your child explain to YOU why he or she was placed there. Do not exceed the timeout time beyond 5 minutes, and do not reward them for behaving in timeout...
I hope this helps...if you need more answers, check out Parenting, it's a great magazine...especially for single moms!